What is the product of the oxidation of ethyl alcohol with $K_2Cr_2O_7$?

Lead pipes are corroded quickly by

Rate of dehydration of alcohols follows the order

The major product $[B]$ in the following reaction is:
$CH_3-CH_2-CH(CH_3)-CH_2-O-CH_2-CH_3$ $\xrightarrow[Heat]{HI} [A] (alcohol)$ $\xrightarrow[\Delta]{H_2SO_4} [B]$

Isopropyl alcohol on oxidation forms

Which of the following gives the most stable carbocation upon dehydration?